Not applicable.
1. Field of the Invention
The present invention relates to an improved furnace roller to advance a metallic workpiece through a reheat furnace and more particularly to a tire construction and securement structure for mounting the tire to an arbor which includes the provision of a core buster for cooling of the arbor.
2. Description of Related Art
Furnace rollers are used to support and guide metallic workpieces through a furnace. U.S. Pat. No. 4,991,276 discloses of one type of furnace roller that is applicable to the present invention. The furnace roller includes a plurality of wheel members welded at spaced apart locations along to an outer tubular member used to form the arbor. The wheel member includes inner hub sections formed of a plurality of angularly spaced-based members. Each base member has a toe portion and head portion separated by a gap extending in the direction of the arbor. A short length of weld at the lateral side of each toe portion interconnects the toe portion to the outer tubular member. The head portion is unattached and free to slide relative to the outer tubular member of the arbor in response to the effect of differential expansion caused by a relatively large thermal gradient in the roller and the bending effect by the weight of the strip upon the roller. A web portion extends from each base member. Each web portion is angularly separated from an adjacent web section by an elongated open space that projects outward slightly short of the inner radius of the rim. The open space further serves to reduce and impede heat flow to the arbor by way of the base member. Apertures are provided in the web portion to provide passage for metal rods used to secure a complement of thermally-insulating discs between the wheel members and thereby provide thermal protection from the high temperature environment in the furnace.
A different furnace roller construction uses castable refracting to form the insulation barrier between wheels is initially covered with a thermal resistant insulating material as disclosed in U.S. Pat. No. 5,230,618. When the roller is used in furnaces operating at approximately 2000xc2x0 F. or higher, the insulating material can be damaged and separate from the roller in the vicinity of a tire the edge by a terminal or leading edge of a strip. Exposure of the tire""s radial sides to the furnace operating temperatures causes thermally induced metal fractures to occur between the open spaces and apertures in the wheel hub. When multiple fractures between the open spaces and apertures the fractures lead to the separation of the rim from its hub.
Research into the causes of the metal fracture led to the apertures and constructing the head portions of the base members flush with the hub. With furnaces operating at temperatures above 2100xc2x0 F., this design results in occasional fracturing across the tire""s rim without protective insulating material. One particular thermal study of this furnace roller in a 2100xc2x0 F. atmosphere with the toe portion of the base member welded to a water-cooled shaft revealed the following conditions. The rim temperature was 2026xc2x0 F. with a radial displacement of the rim equal to 0.1228-inch on its radius. The temperature of the toe portion at the weld connection to a watered-cooled shaft was 400xc2x0 F., with a displacement of 0.008-inch and a bending stress in the base member of 76,212 psi. With this configuration, the 400xc2x0 F. base members restrain the wheel rim from expanding. This phenomenon accounts for the rim fractures observed in actual furnace operations. An advantage exists, therefore, for a tire that will permit the rim to expand to prevent rim fractures from occurring when operating in an environment with temperatures above 2000xc2x0 F. The use of weld metal to establish a metal-to-metal connection between the wheels and the arbor of a furnace roller when eliminated will permit the wheel""s rim to expand when operating in the extreme temperature environment to which reference has been made.
It is therefore an object of the present invention to provide an improved tire that eliminates the base member with direct toe connection of the tire to the shaft of the furnace roll and allows the rim of the tire to expand to prevent fractures from occurring when operating in the extreme temperature environment to which reference has been made.
It is another object of the present invention to provide improved furnace rollers using the improved tires of the present invention that will allow operation of the rollers in the extreme temperature environment to which reference has been made for long periods of operating times without fracturing of the tires.
More particularly according to the present invention there is provided a cast tire for use in a furnace roller to support and advance a workpiece in a furnace, the cast tire including, a rim portion having an annular peripheral tire face to engage and support a workpiece during conveyance thereof in a heated chamber of a furnace, and a continuous web portion having an inner most annular surface contiguous with the outer rim portion, the inner most annular surface defining a load-bearing seat for load-bearing support by an axle, the continuous web having oppositely directed radial face surfaces forming boundaries of angularly spaced pockets bounded by radial edges generally perpendicular to the inner most annular surface, the radial edges being elongated to form moment arms to transmit torque from an applied force by an axle to rotate the continuous web and the rim portion for conveying a workpiece.
The present invention further provides a furnace roller for supporting a workpiece in a furnace, the furnace roller including a rotatable arbor, a number of tires having substantially equal radial extending rim portions at axially spaced apart sites along the arbor for engaging a workpiece, each tire further comprising a continuous web portion having an inner most annular surface contiguous with the outer rim portion, the inner most annular surface defining a load-bearing seat for load-bearing support by an axle, the continuous web having oppositely directed radial face surfaces forming boundaries of angularly spaced pockets bounded by radial edges generally perpendicular to the inner most annular surface, the radial edges being elongated to form moment arms to transmit torque from an applied force by an axle to rotate the continuous web and the rim portion for conveying a workpiece, a plurality of anchor members seated in the pockets and drivingly secured to the arbor for rotation by the arbor; and thermal insulation supported by the arbor to provide a thermal barrier to extend radially between the tires, the insulation having a thickness terminating with an outer surface extending radially at least a substantial portion but less than the entire radii of the tires.